When being involved in a real estate transaction with a Realtor you will be in some form of agency relationship. Just as you are with a lawyer. Only difference is Realtors can represent the same party but with a lawyer it could never happen.
Here is the types of relationships:
Seller Representation: The brokerage is representing the seller, and by law do what is best for the seller. Confidences a seller shares must be kept confidential. The seller agent still must be fair and honest to the buyer and also disclose pertinent information about the property.
Buyer Representation: The brokerage is representing the seller, and by law do what is best for the buyer. Confidences a buyer shares must be kept confidential. The buyer agent still must be fair and honest to the seller.
Multiple Representation: Under this representation the brokerage must do what is best for the buyer and seller. Talk about walking a thin line. This is more the case if the same agent is representing the buyer and seller. It is still multiple representation but if it is two sales representatives with the same brokerage in the transaction they can work as a seller and buyer representation to provide best representations to the parties.
These representations must be under contract to exist. Better known as a listing agreement and a buyers agreement.
Occasionally you will also see:
Customer Service Relationship: No representation is given in this relationship. The brokerage is providing services with no agreement but must still work in a fair and honest manner.
The brokerage always will disclose these relationships to each the buyer and seller.